One of the primary military purposes of beachable marine vehicles is to transport cargo such as vehicles and troops from ships at sea to beachheads. These beachable marine vehicles also have commercial application where they may transport cargo to unimproved beach areas. The U.S. Navy has workhorse vessels for this purpose such as the LCU (Landing Craft Utility) and related marine vehicles. The LCU is an almost flat bottomed monohull which is necessary so that it can drive on and off of beachheads; however, this design makes the LCU and its brethren very uncomfortable in rough seas. A further and most significant shortcoming of the LCU is that it has limited speed capabilities. In the cast of the LCU, the loaded top speed is only 9–12 knots.
A more recent development than the LCU is the LCAC (Landing Craft Air Cushion). The LCAC is a SES (Surface Effect Ship), also known as a hovercraft, with a pressurized air cushion that supports the full vehicle weight. The LCAC has a flat cargo deck with a blower pressurized air cushion underneath that is surrounded by 360 degrees of flexible skirts or seals. As such, the LCAC can run up onto beaches with limited slopes and is therefore fully amphibious. The LCAC has speed capabilities in the 45 knot area but has very limited rough sea capabilities. Further, the gas turbine powered LCAC is very expensive to start with, has a high fuel burn rate, and its flexible full perimeter skirts are high maintenance and expensive to replace.
These preceding noted limitations of current landing craft designs, such as the design concepts incorporated into the LCU or the LCAC, make them inappropriate for the Army TSV (Theater Support Vessel), the Navy and Marine Corps Sea Basing program HSC (High Speed Connector), the Navy Fleet Readiness and Logistics Office, and Naval Sea Systems Command (NAVSEA) RSLS (Rapid Strategic Lift Ship), or the Navy LCS (Littoral Combat Ship).
The TSV must transit oceans on occasion so a rather large high speed and seaworthy vessel is required. The Army has tested existing commercial passenger/vehicle catamaran ferries for the TSV program and they do show some promise but are not beachable due to deep draft requirements.
In the case of the Sea Basing program large parent ships are stationed 100 to 200 miles offshore so a HSC design that offers high speed and beachability to run between these parent ships and beachheads is demanded. There are a number of HSC sizes required with the smallest being about 170×50 feet and capable of transporting over 200 tons of cargo at 40 knots or more.
The RSLS must have trans-oceanic capabilities with one of its primary missions being to transport large CH-53 Super Stallion and other helicopters to world trouble spots and, after delivering the helicopters from an on-board helicopter pad, be able to support hostile beachheads. The RSLS must also be able to, along with the helicopters, transport up to 1,000 troops and their equipment including armored vehicles, supply containers, and the like.
The LCS is a high speed combatant that will operate in enemy littorals. It is somewhat smaller than a destroyer but quite capable as a small combatant. The LCS project is currently in the final design stages with two designs under consideration. The first is a monohull and the second a trihull with a long slender main hull and outrigger hulls either side. Neither of the two competing LCS designs have the advantages of an air cushioned hull as does the instant invention. These advantages include: 1) Beachability, 2) Extreme shallow draft, 3) Reduced underwater magnetic signature, and 4) Reduced shock loads on the hull structure in the event of an underwater blast proximal the hull.
The inventive beachable high speed marine vehicle proposed herein meets the requirements of the TSV, HSC, HSLS, and LCS as well as any other military or commercial requirement where a very efficient, high speed, seaworthy, and beachable marine vehicle is required. While many sizes of the instant invention are feasible, a particular size of the instant invention that meets the requirements of the TSV, a large size HSC, HSLS, and LCS has been subject to preliminary design studies. Based on the requirement that it have a beam of less than 105 feet so that it will pass through the Panama Canal, the selected design is approximately 360×104 feet and can transport 1,000 tons of cargo and fuel at speeds of 40–50+ knots. The instant invention is timely and offers service required features that cannot be provided in combination by other marine vehicles.